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From: email@example.com (Marlboro)
Subject: Re: OPA627 - Is this proper?
Date: 31 Oct 2002 10:49:45 -0800
NNTP-Posting-Date: 31 Oct 2002 18:49:45 GMT
Daniel Haude wrote in message news:...
> over the last years I've built a few preamplifier units utilizing the
> OPA627BM part by Burr-Brown. In order to keep the opamp cool, I clamped
> its TO casing into a metal bracket which in turn was screwed to the casing
> (which is connected to ground).
> This always worked fine. Now a colleague of mine tried to rebuild the unit
> using an opamp from a newer batch. He managed to fry it. I told him how
> expensive the damn things were. He took a new one. Fried it. I told him
> again how expensive they were, adding an appropriate comment about his
> competence (Unlike me, he'd been using all sorts of proper anti-static
> precautions). Put the old part back in, all went fine.
> He checked the data sheet. Found out that the Opamp casing was connected
> to negative supply voltage. I concluded that he must have blown the
> bonding wire from -Vs pin to chip/casing and suggested to connect -Vs to
> the case (without mounting it to the grounded enclosure). Part worked
> My question: I'm sure that when I built the first units years ago I made
> sure that there wasn't supposed to be a connection between the case and
> anything else. Wouldn't I? Anyway, the device worked fine for years and
> still does (so it can't be that the case-ground connection was made only
> recently by accident). Sadly I can't find the old datasheet from back then
> any more.
> So they must have changed the manufacturing process, changing some vital
> electrical specs on the way.
> My question: Is it common for such things to occur? Have similar things
> happened to anybody else?
> --Daniel (more curious than aggravated)
not surprise, we've seen that many times. I believe if you read the
spec carefully, somewhere it would says "...reserve the right to make
changes in this device without further notice..."
So be prepare and call your insurance agents
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